fix: refresh sidebar and navigate away after worktree deletion (#315)

[sauravpanda]

Summary

• After deleting a worktree, the UI now checks if it was the currently selected one
• If so, clears selection (selectedWorktreeId/Path/Name → null), navigating user to home view
• The worktree list was already refreshing on delete — only the selection cleanup was missing

Closes #315

Test plan

• Delete a worktree that is currently selected → view switches to home
• Delete a worktree that is NOT selected → sidebar updates, current view stays

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